1. Field of the Invention
The present invention relates to an elastic wave apparatus in which an elastic wave filter chip including first and second bandpass filters is mounted on a mounting substrate.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2014-17537 discloses a duplexer that is used in an RF (Radio Frequency) stage of a cellular phone. The duplexer includes a transmission filter configured by an elastic wave filter having a ladder circuit configuration. In the elastic wave filter having the ladder circuit configuration, an inductor is connected between parallel arm resonators and a ground potential. The inductor is provided in a package substrate on which a duplexer chip is mounted.
Japanese Unexamined Patent Application Publication No. 2012-156741 discloses that a narrow pitch portion is provided in an elastic wave resonator of a ladder elastic wave filter. Isolation characteristics are improved by providing the narrow pitch portion.
An elastic wave filter apparatus in which one ends of a plurality of bandpass filters are commonly connected, such as a duplexer, is required to have preferable isolation characteristics. In the duplexer having the ladder elastic wave filter, which is disclosed in Japanese Unexamined Patent Application Publication No. 2014-17537, adjustment of an electrode shape as disclosed in Japanese Unexamined Patent Application Publication No. 2012-156741 is generally performed as a method for improving the isolation characteristics.
The adjustment of the electrode shape causes an increase in loss, however. Accordingly, it is difficult to achieve both of an improvement in the isolation characteristics and a decrease in the loss.